Session Drummer 3 random dropouts

Hi all -- With Session Drummer 3/Sonar 8.5, when I assign a MIDI track to Session Drummer, and then playback, notes in the track will randomly play or not -- as in, sometimes the kick will play, sometimes it won't, sometimes the snare will sound, sometimes, not, and so, for any note/drum. It doesn't seem to be a question of CPU availability, since the CPU meter is hovering around 25-30% utilization. 

Anyone have any experience w/ this? It's baffling...(and Cakewalk tech-support, unsurprisingly, has yet to get back to me, three days later.)
Thanks!
--Jack

Thanks, jayson -- that absolutely did the trick. :)

Thanks jayson! We were tearing our hair out here last night trying to figure this out and your fix worked. Weird thing is that the X1 help file says that the default midi playback buffer setting is 500 milliseconds, but mine was set at 250, although I've never touched it. Changing it to 500 took care of the problem.